Interference of diltiazem with serotonin- and potassium-induced contractions in human placental veins.
1. In segments of human placental veins precontracted with K+ (25, 40 or 75 mM), diltiazem produced concentration-dependent relaxations with similar EC50 values. 2. Diltiazem (20 min preincubations) also caused concentration-dependent inhibition of the contractions induced by K+ (40 or 75 mM) and 5-HT (serotonin, 3 x 10(-7) M). IC50 values were similar, in both cases. 3. The time-course of the vasocontractions induced by 75 mM K+ and 3 x 10(-7) M 5-HT in the absence and in the presence of diltiazem were different. The contractions caused by K+ were sustained and transient those elicited by 5-HT. 4. These data suggest that (1) this vasculature is sensitive to diltiazem, and (2) the Ca influx through voltage-operated Ca channels (activated by K+) and through receptor-operated Ca channels (activated by 5-HT) is very similar.
Marín
J
J
Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.
Fernandez-Alfonso
M S
MS
Reviriego
J
J
Guerra
P
P
D004110:Diltiazem / Q000494:pharmacology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010920:Placenta / Q000098:blood supply; D011188:Potassium / Q000494:pharmacology*; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology*
D012701:Serotonin; D004110:Diltiazem; D011188:Potassium